ELECTROLYTE, SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND ELECTRIC APPARATUS

1 . An electrolyte for lithium-ion secondary battery, comprising:

a solvent;

an additive composition; and

a lithium salt;

wherein the additive composition comprises a compound of formula I and at least one of compounds of formula II and formula III:

wherein R 1 , R 2 , and R 5 are each independently H or F, and at least one of R 1 , R 2 , and R 3 is F;

wherein R 4 and R 3 are each independently hydrogen, vinyl, allyl, oxyvinyl, or oxyallyl, and at least one of R 4 and R 5 is not H; and

wherein R 6 , R 7 , R 8 , and Ry are each independently selected from one or more of allyl, vinyl, or allyl butyl.

2 . The electrolyte according to claim 1 , wherein:

the compound of formula I is:

the compound of formula II is:

and

the compound of formula III is:

3 . The electrolyte according to claim 1 , wherein percentage of the compound of formula I in the electrolyte is a wt %, and percentage of the compound of formula II, the compound of formula III, or a mixture of the two, in the electrolyte is b wt %, wherein

0.05

≤

a

/

b

≤

4.

4 . The electrolyte according to claim 1 , wherein percentage of the compound of formula I in the electrolyte is a wt %, and percentage of the compound of formula II, the compound of formula III, or a mixture of the two, in the electrolyte is b wt %, wherein

0.1

≤

a

+

b

≤

10.

5 . The electrolyte according to claim 1 , wherein percentage of the compound of formula II, the compound of formula III, or a mixture of the two, in the electrolyte is 0.06 wt % to 8 wt %.

6 . The electrolyte according to claim 1 , wherein the solvent is a non-protonic organic solvent, the non-protonic organic solvent being selected from one or more of fluorinated and non-fluorinated cyclic and chain organic carbonate, fluorinated and non-fluorinated ether, fluorinated and non-fluorinated cyclic ether, fluorinated and non-fluorinated carboxylic acid ester, and fluorinated and non-fluorinated chain sulfone or cyclic sulfone compounds.

7 . The electrolyte according to claim 1 , wherein the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluoroxalate borate, lithium dioxalate borate, lithium difluorophosphate, lithium difluoro(dioxalato)phosphate, and lithium tetrafluoro oxalato phosphate.

8 . The electrolyte according to claim 1 , wherein in the electrolyte:

the solvent is 60 wt % to 85 wt %.

the additive composition is 0.01 wt % to 20 wt %, and

the lithium salt is 10 wt % to 40 wt %;

wherein a total weight of the foregoing components is 100 wt % and each wt % is based on a total weight of the electrolyte.

9 . A secondary battery, comprising:

the electrolyte according to claim 1 .

10 . A battery module, comprising the secondary battery according to claim 9 .

11 . A battery pack, comprising the battery module according to claim 10 .

12 . An electric apparatus, comprising the secondary battery according to claim 9 .